CAPITAL —AlGhad— At least 10 people have been killed in explosions at underground stations in St Petersburg, Russian media report, and more than 50 were injured, in what seems to be caused by at least one unmanned explosive device filled of shrapnel.

News agencies reported the blasts hit the Sennaya Ploschad and nearby Tekhnologichesky Institut stations in the centre of the city.

Images posted on social media showed a badly-mangled carriage in Sennaya station, with casualties nearby.

President Vladimir Putin said all causes, including terrorism, were being investigated.

The Interfax and RIA news agencies reported that at least 50 people had been injured, and that a number of children were among those hurt.